1. Field of the Invention
The invention generally relates to power line communications (PLC), and more particularly, to exploiting a power line inductive coupler for measuring power frequency current on a power line, and transmitting the measurement over a PLC network of which the same inductive coupler is a component.
2. Description of the Related Art
In a power line communication system, power frequency is typically in a range of 50-60 Hertz (Hz) and a data communications signal frequency is greater than about 1 MHz, and typically in a range of 1 MHz-50 MHz. A data coupler for power line communications couples the data communications signal between a power line and a communication device such as a modem.
An example of such a data coupler is an inductive coupler that includes a core, and a winding wound around a portion of the core. The core is fabricated of a magnetic material and includes an aperture. The inductive coupler operates as a transformer, and is situated on the power line such that the power line is routed through the aperture and serves as a primary winding of the transformer, and the winding of the inductive coupler serves as a secondary winding of the transformer. The data communications signal is coupled between the power line and the secondary winding via the core. The secondary winding is coupled, in turn, to the communication device.
One technique for measuring power frequency current in the power line is to employ a current transformer coupled to the power line, where the current transformer has a secondary short-circuited through an ammeter or other current sensing device. Alternatively, in a case of an open-circuited secondary, a primary current induces a secondary voltage proportional to the primary current.